The disclosure relates to an image forming apparatus.
In electrophotographic printing, the gloss level of an image is a factor determining image quality. In general, image quality is considered to be high when the gloss level of a toner surface (image portion) on a recording medium is not significantly different from the gloss level of the recording medium itself (non-image portion).
This is because the gloss level of the image portion excessively lower than the gloss level of the non-image portion leads to a visually dull impression. In contrast, the gloss level of the image portion excessively higher than the gloss level of the non-image portion leads to an increased amount of reflected light. In this case, the image is difficult to view, and particularly for a document image, characters are difficult to read. Furthermore, the gloss level depends significantly on the type of the recording medium used. For example, the gloss level increases and decreases consistently with the smoothness of the surface of the recording medium.
To deal with such a problem, a technique has been provided in which the thickness and gloss level of the recording medium are detected so that a fixation condition is changed in accordance with the thickness and gloss level, thus allowing the gloss level to be controlled for a variety of recording media. With this technique, however, the fixation condition does not reflect the actual image gloss level after fixation.
In contrast, another technique allows sensing of the gloss level of a toner image portion fixed on the recording medium and of a non-image portion with no toner image. This technique involves setting an appropriate gloss level reference value for the image portion in association with the gloss level of the non-image portion and controlling the fixation condition so that the gloss level of the image portion falls within the range of the reference value. Even when images are formed on a recording medium with a different surface gloss or smoothness level, this control allows images with a gloss level appropriate to the recording medium to be output.